A multimode wireless communication terminal device may comprise a plurality of wireless communication units for different wireless communication networks. The multimode wireless communication terminal device may communicate with a first wireless communication network using a first wireless communication unit, while a second wireless communication unit searches for a second wireless communication network to designate as a candidate network for a handover. When a handover factor (e.g., low signal to noise ratio) occurs, a handover is executed from the first wireless communication network to the second wireless communication network. The multimode wireless communication terminal device executes a handover after the second wireless communication unit establishes a network link to the second wireless communication network. As a result, a seamless handover can be realized without an interruption of communication.
However, power is continually supplied to the second wireless communication unit even when it is not performing communication with any communication network. Also, even when no handover factor occurs, the second wireless communication unit searches for a wireless communication network to become a handover destination, which causes excessive power consumption. As a result, available battery time is shortened.
In addition, a transmission power of the wireless communication terminal device is generally controlled in accordance with a communication status of a corresponding base station. Also, a set value of the transmission power is generally high in a fringe area where a handover factor occurs. Furthermore, an area near the fringe area where a handover factor occurs is often an area near a fringe area for a base station of another wireless communication network where the multimode wireless communication terminal device can execute a handover. In that case, the multimode wireless communication terminal device searches for a candidate base station to be a handover destination while power is continually supplied to one or more wireless communication units that may not be performing communication with any communication network. Furthermore, in an attempt to register its position, the multimode wireless communication terminal device transmits device and other related registration information at high transmission power from the one or more wireless communication units to the candidate base station. Accordingly, a large amount of power is used in the plurality of wireless communication units until the handover is completed. As a result, the amount of power used increases, which causes further exhaustion of the battery.
Therefore, there is a need for a wireless communication terminal device operable to execute a handover between different wireless communication networks with less exhaustion of a battery.